Pile resistor



y 1958 L. H. BERKELHAMER 2,844,692

PILE RESISTOR Filed May 19, 1953 2 Sheets-Sheet 1 IN V EN TOR.

y 1958 L. H. BERKELHAMER 2,

PILE RESISTOR Filed May 19, 1953 2 Sheets-Sheet 2 W fi 75 1a IN V EN TOR.

United States Patent PILE RESISTOR Louis H. Berkelhamer, Chicago, Ill., assignor to David T. Siegel, Glencoe, Ill.

Application May 19, 1953, Serial No. 356,070

Claims. (Cl. 201-63) The present invention relates to electrical resistors, and more particularly to pile wound resistors. The novel features of this invention are particularly useful for,

but not necessarily limited to, the type of pile Wound resistors which include a plurality of coils wound on a core and separated by radially extending flanges.

In the manufacture of resistors of the above described general type, lead wires connecting the coils with each other and with the resistor terminals are generally passed through a slot in the flanges and then inwardly along the side of the flanges to the core and to the initial turns of the coils. These lead wires often become damaged or broken because too great a' tension is placed thereon, or because of an abrasive action on the portion of the leads extending along the sides of the flanges, which abrasive action takes place when the wire is wound on the core. Prior art attempts to eliminate such damage to the wires have been relatively complicated and expensive, and, therefore, it is an object of this invention to provide a novel resistor of the above described type, which resistor may be readily and economically manufactured in a manner to prevent damage to the lead wires.

Another object of this invention is to provide a novel resistor of the above described type wherein adjacent coils are wound in opposite directions to minimize inductance and wherein the lead wires between adjacent coils are arranged and held in a novel manner so as to prevent possible injury thereto.

The cores for electrical resistors of the above described type are generally constructed of an insulating ceramic material, and end terminals for the resistor are generally mounted adjacent, but spaced from, the ends of the core. One form of end terminal has included an annular body section adapted to be placed over the end of the core and a deformable tab on the body section, which tab when pushed inwardly engages the core to retain the body section thereon. In the past, difficulty has been encountered in assembling such end terminals since, if the tab cannot be pushed to its holding position easily, the ceramic core may be broken, and if it is not deformed all the way to its holding position, insuflicient clearance may result between the tab and the end of the core to provide an adequate insulating space between the tab and other parts of the apparatus to which the resistor may be attached. It is, therefore, another object. of this invention to provide an end terminal having a novel locking tab which may be readily pushed all the way to its locking position without danger of breaking the ceramic core.

Still another object of this invention is to provide novel means for connecting the lead wires with the end terminals of the resistor so the connection is protected against accidental breakage by any cause such as a tool being used by a workman to install the resistor.

-Still another object of this invention is toprovide novel means for connecting the lead wires to the end terminals so that there is a predetermined slack in the lead Patented July 22, 1958 wires, thereby preventing the wires from being broken because of excessive tension therein.

Still another object of the present invention is to provide a novel method for manufacturing resistors of the above described type by which method the coils of the resistor may be wound without danger of injuring the connecting lead wires.

Other objects and advantages of the present invention will become apparent from the following description and the accompanying drawings, wherein:

Fig. 1 is a perspective view, showing a resistor embodying the principles of this invention;

Fig. 2 is a cross sectional view taken along line 2-2 in Fig. 1;

Fig. 3 is a transverse cross sectional view taken along line 3-3 in Fig. 2;

Figs. 4, 5, 6, and 7 are fragmentary perspective views illustrating the novel steps for winding the coils of the resistor of this invention; i

Fig. 8 is an enlarged fragmentary cross sectional view illustrating the manner in which the lead wire joining adjacent coils is positioned and held;

Fig. 9 is an end view of a resistor embodying the principles of this invention;

Fig. 10 is a fragmentary side elevational view showing the novel means for connecting the lead wire to the end terminal in an intermediate state of assembly;

Fig. 11 is similar to Fig. 10, but showing the connecting means in its finally assembled position;

Fig. 12 is a fragmentary cross sectional view showing the novel end terminal of this invention at an intermediate stage of assembly;

Fig. 13 is similar to Fig. 12, but shows the novel end terminal of this invention fully assembled with the core;

Fig. 14 is a perspective view, showing the novel end terminal of this invention;

Fig. 15 is an enlarged fragmentary cross section taken along line 1515 of Fig. 9; and

Figs. 16 and 17 are, respectively, a perspective view and an edge view illustrating a modified terminal element of this invention.

Referring now more specifically to the drawings, wherein like parts are designated by the same numerals throughout the various figures, a resistor 20 embodying the principles of this invention is shown in Fig. 1. The resistor 20 includes a core 22 made of an insulating material and preferably a ceramic material. If desired, the core 22 may be provided with a longitudinally extending bore 24. Adjacent the ends of the core is a pair of radially extending end flanges 26 and 28, and between these flanges a plurality of radially extending separator flanges 30, 32, and 34 are spaced evenly axially of the core. Preferably, these flanges are formed integrally with the core 22. Between adjacent flanges, wire coils 36, 38, 40, and 42 are wound on the core. These coils are wound with a wire having a coating of any suitable insulating material thereon.

The adjacent coils are connected by lead Wires 44, 46, and 48, and the end coil 36 is connected with a sheet metal end terminal 50 by a lead wire 52, and the opposite end coil is connected with an opposite sheet metal end terminal 54 by lead wire 56. It is understood, of course, that the lead wires and coils are preferably formed from a single length of any suitable wire.

In order to provide a passageway for the lead wires to extend from the end terminals to the coils and from one coil to another, the flanges 26 through 34 areprovided with radially extending slots or openings 58, 60, 62, 64, and 66, respectively. Referring more specifically to Figs. 2, 3, and 8, it should be noted that the openings have bottom surfaces which are flush with the outside surface of the core 22. In addition, the core is preferably constructed so that it'has a uniform diameter between the flanges.

The novel method and means for winding the coils of this invention and for locating and holding the lead wires between the coils is illustrated best in Figs. 4 through 8. Referring particularly to Fig. 4, it will be noted that the coil 36 has been wound in a counterblockwise direction and that the coil terminates at a point 68 disposed on one side of the flange 30 and spaced radially outwardly from the surface of the core 22. From this point 68, wire is directed through the opening 62 in the flange 30 so that the lead wire 44 extends crosswise from one side of the opening toward the other side and over an elongated strip 70, which may be of any suitable material, such as an adhesive tape of silicone glass or the like. This strip 70 is shown best in Fig. 2 and extends from one end of the core to the other through the openings or slots in the flanges. After the wire has been disposed as shown in Fig. 4, the free end of the tape 70 is pulled upwardly and rearwardly through the opening in the flange, as shown in Fig. 5, and then the wire is passed beneath the strip, as shown in Fig. 6. The strip 70 is then again placed flat against the surface of the core 22, and the wire is wound in a clockwise direction around the core and over the strip, as illustrated in Fig. 7, to form the coil 38. The strip or tape 70 holds the lead wire 44 with a predetermined tension so that the subsequent winding operations cannot materially increase the tension in the lead, whereby the possibility that the lead will be broken is materially reduced. Furthermore, the strip 70 holds the lead so that it is directed against the bottom of the opening 62, whereby as the lead wire emerges from the opening, it is flush against the surface of the core so that no abrasive action occurs during the subsequent winding of the wire to form the coil 38. This structure is shown best in Fig. 8, wherein the lead wire 44 is illustrated as being disposed entirely within the confines of the flange 30 and held against the bottom surface of the opening in the flange at a point spaced inwardly from the coil 38. Furthermore, because the lead wire passes over and then under'the strip 70, the coil 38 may be wound in a direction opposite to the direction of the winding of the coil 36 without danger of injuring the insulation on the wire. This results from the fact that the wire is bent around the relatively soft strip 70 rather than sharply around the relatively hard corners of the flange 30.

The novel manner in which the lead 52 is connected with the end terminal 50 is illustrated best in Figs. 9, 10, 11, and 15. This means includes a deformable metal finger 72 which is secured adjacent one end thereof as by soldering or welding to an annular body portion 74 of the end terminal. As shown in Fig. 10, the finger 72 is initially formed so that its free end extends generally axially away from the end terminal, and the lead 52 is wound two or three turns about the axially extending portion of the finger and then welded, as at 76, to the finger. The finger 72 is then deformed so that it lies substantially flat against the end terminal, as illustrated in Figs. 9, 11, and 15. It should be noted that the weld 76 is located on the side of the finger that is pressed against the end terminal so that the weld is protected against inadvertent damage. In addition, when the finger is deformed against the end terminal, the lead 52 is loosened or given a certain amount of slack so that the lead wire cannot be broken because of undue tension therein.

The lead wire 52 extends between the end terminal and the coil 36 in much the same manner as the lead wire 44 extends between the coils 36 and 38. Thus, the lead wire 52 is directed inwardly through the central aperture of the annular body 74 of the terminal, as shown best in Fig. 15, thence through the opening 60 in the end flange 28, and under the strip 70 so that the lead emerges from the opening 60 in the flange 28 flush with the surface of the core 22. The core 22, which has an enlarged end 78 (see Figs. 12 and 13), for a purpose more fully described 4 below, is slotted as at to permit the passage of the lead wire 52 from the finger 72 to the opening in the end flange. It is understood, of course, that the lead wire 56 is connected to the end terminal 54 at the opposite end of the resistor by a deformable finger which is substantially identical to the above described finger "/"2.

The end terminals 50 and 54 are substantially identical, and, therefore, only the novel features of the terminal 50 will be described in detail. As set forth above, the end terminal 50 includes an annular body section 7 4, which is adapted to fit over the end of the core. An extension 81 projects radially from the annular body section for connection with any suitable electric lead. The aperture through the annular body section preferably has a diameter which is substantially equal to the outside diameter of the enlarged end 78 of the core 22. The core 22 is provided with an annular groove 82 which provides an inwardly directed radially extending shoulder adapted to overlie and engage an inner marginal edge portion of the annular body section 74, as shown in Figs. 12 and 13. A deformable tab 84 extends radially inwardly from the inner margin of the annular body section for locking the end terminal on the end of the core. This tab preferably is formed with an arcuate head joined with the body section by a relatively narrow neck, which neck is formed by cutting away the material of the body section and tab, as at 86 and 88.

When assembling the end terminal 50 with the core, the annular body section is passed over the enlarged end of the core until the end terminal rests on the end flange 28. The end terminal is then moved so that an inner marginal edge portion thereof opposite from the tab 84 enters the groove 82 in the core. The enlarged end of the core is provided with an axially extending slot 90, shown best in Fig. 1, for receiving the arcuate head of the tab 84. The slot 90 is formed so that the distance between is innermost surface and the bottom of the groove 82 at the opposite side of the core issubstantia'lly equal to the distance between the free edge of the tab 84 and the opposite inner edge of the annular body section. Thus, when the tab 84, which is initially in the position shown in Fig. 12, is bent downwardly to the plane of the body section 74, as shown in Fig. 13, the inner marginal edge of the body section is securely locked within the groove 82. It should be noted that the end terminal 50 is spaced a predetermined distance from the end of the core in order to provide a suflicient insulating air space between the terminal and the apparatus to which the resistor may be mounted. If for any reason the tab 84 is not bent to the full locking position shown in Fig. 13, the distance between the end of the tab and the end of the core may be in'suflicient for adequate insulating purposes. Due to manufacturing inaccuracies and various other reasons, it often happens that the end of the tab 84 engages the bottom of the slot 90 before the tab has reached the full locking position. If undue pressure is exerted to force the tab to the position shown in Fig. 13, breakage of the ceramic core may occur. However, in accordance with the present invention, the possibility of such breakage is materially minimized by reason of the particular form of the tab, which includes the narrow and relatively easily deform-able neck portion. Thus, when the tabs 84 of this invention engage the core before they are fully seated, a relatively small additional pressure causes the relatively narrow neck to buckle sufiiciently to enable the tab to be bent to its full locking position without danger of breaking the ceramic core. After the resistor has been assembled as described above, it may be coated, if desired, with any of the well known impregnating materials in any suitable manner, such as by dipping the unit into a bath of the impregnating material. If required, the impregnated unit may then be baked in an oven in the usual manner.

In Figs. 16 and 17, there is illustrated a modified end terminal 50a which is substantially identical to the termiwire 52 will be spot welded directly to the body section 74.

When attempting to weld the fine wire 52 to the relatively broad flat surface of the body section 74, it has been found that a satisfactory weld is sometimes difiicult to obtain since a precise point of good contact between the wire and the broad flat surface of the body section 74 cannot always be determined. Therefore, in accordance with a feature of this invention, the body section 74 of the terminal 50a is provided with an embossed protuberance 96 with a relatively pointed or sharp edge 98. By placing the lead-wire 52 over the sharp edge of the protuberance 96, a satisfactory weld is assured since the precise point of good contact between the wire and the terminal is definitely determined. There are many instances when the terminal 50a may be substituted for the terminal 50, and in such instances, the terminal 50a has the advantage of simple construction and economical manufacture. I

From the above description, it is seen that the present invention has provided a novel resistor and method of making the same, whereby the resistor may be economically and readily manufactured in a manner to prevent injury to. the lead wires. More particularly, means is provided for winding the several pile sections in a manner so that the insulation is preserved on the wire at all times, abrading action being eliminated. Also undue tension in and breaking of the connecting wire between the pile sections is eliminated- In addition, it is further seen that the novel end terminals of this invention may be simply and economically manufactured and readily applied to the ceramic cores without danger of breaking the cores. Furthermore, it will be appreciated that the novel means for connecting the lead 'wires to the end terminals enables 'the wires to be quickly and easily connected because of the projecting fingers and provides a secure connection which is protected against damage, and wherein a predetermined slack is introduced into the wire as the connection is completed to prevent wire breakage.

While the preferred embodiment of the present invention has been shown and described herein, it is obvious that many changes may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. An electrical ressitor, comprising a core, a plurality of flanges extending radially from said core, each of said flanges having an opening therethrough with bottom surfaces, a strip of material extending along the surface of said core and the bottom surfaces of said openings, a plurality of wire coils having superimposed turns wound on said core between said flanges, lead wires connecting an outer turn of at least some of said coils with an inner turn of adjacent coils, said lead wires being directed through the opening in the flange between the adjacent coils, and a portion of each of said lead wires being directed against the bottom surfaces of said openings and beneath said strip of material so that said strip of material holds said portions of the lead wires against said bottom surfaces in the desired position. 1

2. An electrical resistor, comprising a core, a pair wire coils having a plurality of turns wound on said core, one of said coils being wound in a clockwise direction and the other of said coils being wound in a counterclockwise direction, a flange disposed between said coils and extending radially from said core, said flange having an opening therethrough with a bottom surface, a strip of material extending generally axially along the surface of said core and over the bottom surface of said opening, a lead wire extending through said opening and connecting said coils, and said lead wire being disposed so that a portion thereof crosses over said strip of material and thence under said strip of material so that the strip of material holds the lead wire in the desired position and out of relatively sharp bending contact with the edges of said flange.

3. An electrical resistor, comprising a core, a wire coil on said core, an end terminal on said core and connected with said coil, said end terminal including an annular body section having an internal diameter largerv than the diameter of said core, said core having an inwardly directed radially extending shoulder adapted to engage an inner marginal portion of said annular body section, and deformable tab means extending from another inn-er marginal portion of said annular body section for engagement with said core to lock said first mentioned marginal portion in engagement with said shoulder, said tab means having an enlarged head for engagement with said core and a relatively narrow easily deformable neck connecting the enlarged head with said annular body section.

4. An electrical resistor, comprising a core, a wire coil on said core, a terminal on said core and connected with said coil, said terminal including an annular body section having an internal diameter larger than the diameter of said core, said core having an inwardly directed radial shoulder for engagement with an inner marginal portion of said annular body section,- and tab means extending from another inner marginal portion of said annular body section for engagement with said core to lock said first mentioned marginal portion in engagement with said shoulder, said tab means and said annular body section being recessed to provide a relatively narrow readily deformable neck joining said tab means with said annular body section.

5. An electrical resistor, comprising a core, a plurality of flanges extending radially from said core, each of said flanges having an opening therein with a bottom surface substantially flush with the surface of said core, a plurality of wire coils having superimposed turns wound on said core between said flanges, a lead wire connecting an outer turn of one of said coils with an inner turn of an adjacent coil, said lead wire'being directed through the opening in a flange between said adjacent coils and against the bottom surface of said last mentioned opening, means for holding said lead wire against said last mentioned bottom surface, a terminal having an annular body section disposed on said core, said core having a shoulder for engagement with an inner marginal portion of said annular body section, adjustable tab means extending radially inwardly from said annular body section for engagement with said core to lock said annular body section in engagement with said shoulder, said adjustable tab means having a relatively narrow readily deformable neck so that said tab means may be easily adjusted to a locking position, a deformable element secured to said body section and having a portion thereof movable toward and away from said body section, and a lead wire connecting said terminal with one of said coils, said lead wire being secured to said deformable element so that upon movement of said deformable element toward said body section, slack is provided for said lead wire.

6. A method of manufacturing an electrical resistor, having a plurality of wire coils on a core provided with a radially extending flange between the coils, which flange has an opening with a bottom surface, said method comprising applying a strip to said core, which strip extends along the surface of said core and the bottom surface of said opening, winding the Wire into a first coil at one side of the flange securing one end of a wire to said core, directing the wire into said opening from an outer turn of said first coil, passing the Wire under a portion of said strip covering a portion of said bottom surface, directing said wire onto the surface of said core, winding a plurality of turns of said wire on the core and over the strip at the other side of said flange and securing the opposite end of the wire to said core.

7. A method of manufacturing an electrical resistor 7 having a plurality of wire coils on a core provided with a radially extending flange separating said coils, which flange has an opening with a bottom surface, said method comprising applying a strip of material longitudinally of the surface of the core and across the bottom surface of the opening in the flange, securing one end of the wire to said core, winding a plurality of turns in one direction on said core to provide one coil, directing the wire into the opening in said flange and transversely of a portion of the strip covering the bottom surface of said opening, passing the wire transversely under a portion of said strip covering said bottom surface, directing said wire onto the surface of said core, and winding a plurality of turns in an opposite direction on the core and over the strip to provide a second coil and securing the opposite end of the wire to said core.

8. An electrical unit comprising a core having a terminal flange at one end thereof with a substantially radial slot in said flange, a terminal member having an attachment extension and a substantially flat body portion adapted to be mounted on said core, a bendable connecting element mounted on said body portion and initially projecting outwardly from said flat body portion, mutually cooperating and interfitting means between the body portion of the terminal member and the core for mounting the terminal member on the core with the body portion of the terminal member disposed exteriorly adjacent said flange and with said connecting element disposed adjacent said slot, and a wire coil Wound on said core with a lead portion extending exteriorly through said slot and connected to said connecting element, said connecting element being deformable toward the slot in finally secured position for providing slack in the wire lead portion extending through the slot.

9. An electrical unit as claimed in claim 8, wherein the body portion of the terminal member comprises a substantially annular ring member with a portion thereof traversing the slot in said flange.

10. An electrical unit as claimed in claim 9, wherein the bendable connecting element is secured to the annular ring member in the vicinity of the portion thereof which traverses the slot in said flange.

References Cited in the file of this patent UNITED STATES PATENTS 1,230,921 Paul June 26, 1917 1,759,184 Bullinger May 20, 1930 1,976,514 Pugh Oct. 9, 1934 1,985,691 Pugh Dec. 25, 1934 1,987,118 Lodge Jan. 8, 1935 2,047,796 Ogg July 14, 1936 2,332,255 Podolsky Oct. 19, 1943 2,406,079 Krueger Aug. 20, 1946 2,407,171 McFarren Sept. 3, 1946 2,547,405 Mitchell et a1. Apr. 3, 1951 2,636,963 Wakefield Apr. 28, 1953 2,652,522 Vanderhoof Sept. 15, 1953 FOREIGN PATENTS 657,421 France July 7, 1928 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,844,692 July 22, 1958 Louis E. Berkelhamer It is herebj; certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line '7, for "counterblockwise" read --counterc1ockwise= column 4, line 36, for "is", second occurrence, read its g column 5, line 48, for "ressitor" read eeresistor column 6, lines 66 and 67,. strike out "Winding the wire into a first coil at one side of the flange" and insert the same after "core in line 67, same column,

Signed and sealed this 14th day oi October 1958@ (SEAL) Attest: KARL H. mm ROBERT c. WATSON Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,844,692 July 22, 1958 Louis H. Berkelhamer It is herebjr certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line '7, for "counterblockwise" read -'-counterclockwise column 4,- line 36, for "is", second occurrence, read its; column 5, line 48 for "ressitor" read le -resistor; column 6, lines 66 and 67,. strike out "winding the wire into a first coil at one side of the flange" and insert the same after "core," in line 67, same column,

Signed and sealed this 14th day of October 1958 (SEAL) Attest:

KARL 1H, AXLINE ROBERT c. WATSON Attesting Oflicer Commissioner of Patents 

